A Microfluidic Mixer to Activate Sperm Cells of Aquatic Species for Standardization of Computer-Assisted Motion Analysis

The objective of this paper is to develop a microfluidic device to: 1) activate a small volume of aquatic species sperm by rapid mixing with diluent, and 2) position sperm in a viewing chamber for motility evaluation using computer-assisted sperm analysis (CASA). Analysis of aquatic species sperm is becoming more important as the use of fish as biomedical models expands. Because it is more efficient to maintain frozen stocks of genetic material rather than thousands of research lines of adult fish, there has been increased study on cryopreservation for model fish. The analysis of fish gametes is challenging due to small sample size, short motility duration, and inconsistent activation (motility induction). For many aquatic species, sperm motility is initiated through the manual alteration of the medium osmolality, typically accomplished through manual dilution and mixing by hand. Manual methods limit control over the activation process and therefore viability analysis. The short lifespan of these cells makes CASA challenging due to the limitations in capturing and processing data rapidly enough to monitor the peak motility, as CASA systems were designed for mammalian sperm which have a longer motility duration.